Impermeable slit-type flexible door



June 9, 1964 M. D. MEARS IMPERMEABLE SLIT-TYPE FLEXIBLE DOOR 2Sheets-Sheet 1 Fig.3

Fig.2

Filed June 15, 1962 INVENTOR Marion 0. Mears ATTORNEY June 9, 1964 M. D.MEARS 3,136,356

IMPERMEABLE sLIT-TYPE FLEXIBLE DOOR Filed June 15, 1962 2 Sheets-Sheet 2INVENTOR Merton D. Mears ATTORNEY United States Patent 3,136,356IMPERMEABLE SLIT-TYPE FLEXIBLE DOOR I Merton D. Mears, Baltimore, Md.,assignor to the United States of America as represented by the Secretaryof the Army Filed June 15, 1962, Ser. No. 202,923 1 Claim. (Cl. 160-87)The invention herein described may be manufactured and used by or forthe Government of the United States of America for governmental purposeswithout the payment to me of any royalty thereon.

This invention relates to an impermeable slit-type flexible door used asa passage into and out of protective shelters with a minimuminfiltration of contaminants. More particularly, the door is designed tostay closed under constant tension in pressurized as well as innonpressurized protective shelters, which is unlike any other known tome. The patent in Flanigan, 2,854,070, is representative of the priorart in this field.

The opened slit of the door conforms, in general, to the shape of aperson passing therethrough thus reducing the tendency for contaminatedair to be carried along. In the closed position, the door leaks verylittle, even under pressures up to one inch water gage.

In a non-pressurized shelter, several doors may be used in seriesbetween the contaminated area and the shelter proper, with compartmentsbetween, to give graduated reduction in the degree of contamination asthe shelter proper is approached. In a pressurized structure, the dooris used in the air-lock.

The invention will be best understood by reference to the accompanyingdrawings forming a part of this specification, and in which;

FIG. 1 is a front view of the subject door.

FIG. 2 shows the door panels spread apart to permit a person to passtherethrough.

FIG. 3 is an enlarged sectional view of the upper panel, showing itcemented onto the door panels.

FIG. 4 is a fragmentary rear view of the door in a closed position.

FIG. 5 is a fragmentary rear view of the door in a partially openposition.

FIG. 6 is an enlarged sectional view taken through section 6-6 showingthe relative position of the panel elements.

FIG. 7 is an enlarged sectional view taken through section 77 showingthe relative position of the panel elements.

FIG. 8 is an enlarged sectional view taken through section 8-8 showingthe relative position of the panel elements in an open position.

FIG. 9 is a schematic representation of forces involved when the door isin the closed position.

FIG. 10 is a schematic representation of forces involved when the dooris in an open position.

The door consists essentially of three panels usually of rubber coatedcloth or sheet plastic; the right door panel 1, the left door panel 2,and the upper panel 3. The right panel 1, and the left panel 2,constitute the door proper generally shown at 5. These two panels areplaced in a plane with their vertical edges meeting in the center of thedoor so that when they are pulled apart they will form or create a slitor opening 11. Each adjacent edge (shown at 7) is cemented or heatsealed around flexible tubing (made of rubber or other resilientmaterial) 13 and 15. The panels 1, 2 have cemented along their entirevertical lengths at seams 17 and 19, flaps 21 and 23. The loose edge offlap 21 extends inwardly beyond the edge 7 containing the tubing whilethe loose edge of flap 23 extends outwardly beyond the edge 7 containingthe tub- 3,136,356 Patented June 9, 1964 ing. This creates a spacebetween the flaps and the panels for the insertion of the tubed edge ofthe opposite panel, so that, when the door is closed the tubed edges,shown at 7, and the flaps 21, 23 of the panels 1 and 2 interlock to forma seal. The boundaries of the seams 17, 19 are in the shape of an are(not shown) with the are being closer to the tubed edges (as shown inFIG. 7)

at their mid points. The purpose of the tubing in said edges and saidarc-shaped seams is to assure positive seal- It is to be noted that thetubing 13, 15 does not extend quite to the extreme upper and lower endsof the door panels (this is not shown) but stops approximately 2 inchesshort from said ends. The edges of the flaps and panels at these endsare cemented and clamped together with rivets and plates 26. The upperpanel 3 is cemented and sealed with the upper end of the panels 1, 2 andfolded (as shown at 24) to allow the top of the door panels to drop asthe panels are parted or opened. A slit is thus formed between thesesecured ends of the panels for passage through the door.

The door panels 1, 2 have at their upper edge a hook and eye 25. Thedoor assembly consisting of the three panels is attached and sealed to arigid frame 27. The frame may be of any material and shape. It may bedesigned to be taken apart or folded.

At. the rear, the door panel assembly has attached thereon aspring-lever means shown at 29. Said springlever means comprises a cable31 having its one end attached to the hook and eye of the door panel,while engaging a pulley 33 it has its other end attached to a lever 35.This lever is through means of pin 37 pivotally fastened to a diagonallypositioned support or bracket 39 which in turn is rigidly fastened tothe frame 27. The lever 35 also has an extension spring 41 which at itslower end is fastened to the frame 27.

In operation, the person entering through the door, pulls apart the doorpanels 1, 2 (at the edges shown at 7) activating the spring-lever meansshown at 29. The spring lever means is designed to exert an upward pullat the top of the door above the slit 11 through means of the extensionspring 41. As the door is opened, by parting the door panels, the forceexerted on the door, through the lever means, decreases and the elfortnecessary to further open the door diminishes. The upper edge of thedoor is brought downwardly, upon parting the door panels, resulting inpulling with it the hook and eye 25 and the cable 31 which engages thepulley 33 pivotally moving the lever 35 in a counter clockwisedirection. The lever 35 is arranged so that the moment around pin 37decreases as the door is opened, thereby reducing the effectiveness ofthe extension spring 41. This pivotal movement of the lever 35 stretchesthe extension spring 41. As the person completes the passage through thedoor, the latter action will be in reverse. When the door is clFsed themovement around pin 37 is such that the maximum tension is exerted onthe door thereby increasing the effectiveness of the extension spring41. The extension spring 41 attached to the frame 27 and to the lever 35exerts a torque on said lever turning same on pin 37 in a clockwisedirection. A force is transmitted along the cable 31 over pulley 33 andto the top of the door through the hook and eye 25 thereby bringing thedoor in a closed position.

This upward vertical force holds the door closed under tension. Thetubed edges (shown at 7) are held under pressure against the (previouslymentioned) arc-shaped seams 17, 19 of the adjacent panel thus sealingthe door. The resultant tension causes the edges along the slit tointerlock and part of the vertical tension is translated into ahorizontal component which exerts pressure between the tubed edges andthe arc-shaped seams (referred to earlier) of the door panels and theflaps. The springlever means is designed to exert the maximum verticalforce on the door at its closed position when sealing is desired. 7 r

In operation, the door is opened just enough to allow the person to passthrough. Upon release, the door automatically closes and seals.

It is to be understood that while the above described spring-lever dooris the preferred embodiment of my device, other means may be employed tokeep tension on the tubed edges 7. For example, the lever 35 could bereplaced by a second pulley. This would destroy the novel features of mydevice set forth above but the sealing of the door Wouldbe approximatelythe same. In like manner, the spring can be replaced with weights ineither of the above modifications, without greatly changing the functionof the door.

The forces exerted on the door are shown diagrammatically in FIGS. 9 and10.

An analysis follows:

Let

T be the torque around fulcrum O F be the horizontal force exerted byspring F be the vertical tension at the top of the door F be thecomponent of F along a F be the component of F along z and represent thehorizontal force or effort required to open the door x be the verticaldistance between fulcrum O and the lin of force of the spring w be thehorizontal distance between the fulcrum O and the line of tension on thedoor a be one half of the height of the door when closed 2 be one halfof the width of the door at its midpoint y be one half of the height ofthe door when opened Then Although the force exerted directly by'thespring is slightly greater as the door is opened, the change of momentsaround 0 results in a decreasing tension on the door and the forceagainst which the door is opened, F is greatly reduced.

As the door closes, the moments around 0 react to greatly increase theeffectiveness of the spring in a vertical tension on the door. As thedimension represented by Z approaches zero, the horizontal force Fapproaches zero. But Z never reaches zero because of the arc designed inthe attaching of the door flaps. Thus, there is always a horizontalforce between and along the flap and the tubed edge of one panel and thetubed edge and the flap of the other panel, assuring a positive seal.

Various modifications and changes in the embodiments of the invention asdisclosed are contemplatedand may obviously be resorted to withoutdeparting from the spirit and scope of the invention as hereafterdefined by the appended claim.

I claim:

An impermeable slit-type door for protective shelters comprising:

a door frame;

a top panel folded over' on itself attached to the top and sides of saidframe on three edges;

two side panels meeting at the centerof said frame to form central edgesand attached to the sides, bottom of said frame and the fourth edge ofsaid top panel; sealing means mounted on said central edges;

tension means mounted on said frame to vertically tension said centraledges comprising:

a mounting bracket attached to said frame;

a lever pivotally attached to said bracket at a point intermediate theends thereof;

a pulley mounted on said bracket vertically above said central edges;

anextension spring attached to said frame and the end of said leverremote from said pivoted attachment;

a cable running from said central edges over said pulley to said remoteend of said lever.

References Cited in the file of this patent UNITED STATES PATENTS2,041,258 Mitchell May 19, 1936 2,321,491 Keys et al. June 8, 19432,560,661 Poovey July 17, 1951 2,854,070 Flanigan Sept. 30, 1958

